Capacitor and capacitor module

ABSTRACT

According to one embodiment, a capacitor includes a conductive substrate, a conductive layer, a dielectric layer, and first and second external electrodes. The conductive substrate has a first main surface provided with recess(s), a second main surface, and an end face extending between edges of the first and second main surfaces. The conductive layer covers the first main surface and side walls and bottom surfaces of the recess(s). The dielectric layer is interposed between the conductive substrate and the conductive layer. The first external electrode includes a first electrode portion facing the end face and is electrically connected to the conductive layer. The second external electrode includes a second electrode portion facing the end face and is electrically connected to the conductive substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. application Ser. No. 16/742,095 filedJan. 14, 2020, and claims the benefit of priority under 35 U.S.C. § 119from Japanese Patent Application No. 2019-020614 filed Feb. 7, 2019, theentire contents of each of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a capacitor.

BACKGROUND

With the downsizing and upgrading of communication equipment, capacitorsto be mounted thereon are desired to be smaller and thinner. As astructure to achieve downsizing and reducing the thickness of thecapacitor while maintaining the capacitance density, there is a trenchcapacitor with an increased surface area made by forming trenches on asubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a capacitor according to a firstembodiment as observed diagonally above;

FIG. 2 is a perspective view of the capacitor shown in FIG. 1 asobserved diagonally below;

FIG. 3 is a top view of the capacitor shown in FIGS. 1 and 2 ;

FIG. 4 is a cross-sectional view taken along a line IV-IV of thecapacitor shown in FIG. 3 ;

FIG. 5 is a cross-sectional view taken along a line V-V of the capacitorshown in FIG. 3 ;

FIG. 6 is a cross-sectional view taken along a line VI-VI of thecapacitor shown in FIG. 3 ;

FIG. 7 is a cross-sectional view taken along a line VII-VII of thecapacitor shown in FIG. 3 ;

FIG. 8 is a cross-sectional view taken along a line VIII-VIII of thecapacitor shown in FIG. 3 ;

FIG. 9 is a cross-sectional view taken along a line IX-IX of thecapacitor shown in FIGS. 1 and 2 ;

FIG. 10 is a cross-sectional view taken along a line X-X of thecapacitor shown in FIGS. 1 and 2 ;

FIG. 11 is a cross-sectional view showing a process in the manufactureof the capacitor shown in FIGS. 1 to 10 ;

FIG. 12 is a cross-sectional view showing another process in themanufacture of the capacitor shown in FIGS. 1 to 10 ;

FIG. 13 is a cross-sectional view showing still another process in themanufacture of the capacitor shown in FIGS. 1 to 10 ;

FIG. 14 is a cross-sectional view showing still another process in themanufacture of the capacitor shown in FIGS. 1 to 10 ;

FIG. 15 is a cross-sectional view showing a structure obtained by theprocesses of FIGS. 13 and 14 ;

FIG. 16 is another cross-sectional view showing the structure obtainedby the processes of FIGS. 13 and 14 ;

FIG. 17 is a cross-sectional view showing still another process in themanufacture of the capacitor shown in FIGS. 1 to 10 ;

FIG. 18 is a cross-sectional view showing an example of a capacitormodule including the capacitor shown in FIGS. 1 to 10 ;

FIG. 19 is a perspective view showing a part of a capacitor according toa second embodiment; and

FIG. 20 is a perspective view showing a process in the manufacture ofthe capacitor according to the second embodiment.

DETAILED DESCRIPTION

A capacitor according to a first aspect comprises: a conductivesubstrate having a first main surface, a second main surface, and an endface extending from an edge of the first main surface to an edge of thesecond main surface, the first main surface being provided with one ormore recesses; a conductive layer covering the first main surface andside walls and bottom surfaces of the one or more recesses; a dielectriclayer interposed between the conductive substrate and the conductivelayer; a first external electrode including a first electrode portionthat faces the end face, the first external electrode being electricallyconnected to the conductive layer; and a second external electrodeincluding a second electrode portion that faces the end face, the secondexternal electrode being electrically connected to the conductivesubstrate.

A capacitor according to a second aspect comprises: a conductivesubstrate having a first main surface and a second main surface, thefirst main surface being provided with one or more recesses; aconductive layer covering the first main surface and side walls andbottom surfaces of the one or more recesses; a dielectric layerinterposed between the conductive substrate and the conductive layer; afirst external electrode including first and second bonding padsrespectively facing the first and second main surfaces, the firstexternal electrode being electrically connected to the conductive layer;and a second external electrode including third and fourth bonding padsrespectively facing the first and second main surfaces, the secondexternal electrode being electrically connected to the conductivesubstrate.

A capacitor module according to a third aspect comprises: a stacked bodyincluding a plurality of capacitors stacked one on top of another, eachof the plurality of capacitors being the capacitor according to thefirst or second aspect, and two adjacent ones of the plurality ofcapacitors being such that the first external electrodes areelectrically connected to each other and the second external electrodesare electrically connected to each other; and a circuit substratesupporting the stacked body.

A capacitor module according to a fourth aspect comprises: a stackedbody including a plurality of capacitors stacked one on top of another,each of the plurality of capacitors being the capacitor according to thefirst aspect; a circuit substrate supporting the stacked body; a bondingmaterial provided to be in contact with the first electrode portions ofthe plurality of capacitors and electrically connecting the firstelectrode portions together; and a bonding material provided to be incontact with the second electrode portions of the plurality ofcapacitors and electrically connecting the second electrode portionstogether.

Embodiments will be explained in detail below with reference to theaccompanying drawings. Note that the same reference numerals denoteconstituent elements which achieve the same or similar functionsthroughout all the drawings, and a repetitive explanation will beomitted.

First Embodiment

FIGS. 1 to 10 show a capacitor according to a first embodiment.

A capacitor 1 shown in FIGS. 1 to 10 includes a conductive substrate CS,a conductive layer 20 b, and a dielectric layer 50, as shown in FIGS. 4to 10 .

In each figure, an X direction is a direction parallel to a main surfaceof the conductive substrate CS, and a Y direction is a directionparallel to the main surface of the conductive substrate CS andperpendicular to the X direction. In addition, a Z direction is athickness direction of the conductive substrate CS, i.e., a directionperpendicular to the X direction and the Y direction.

The conductive substrate CS is a substrate having electricalconductivity at least in its surface. The conductive substrate CSincludes a first main surface S1, a second main surface S2, and endfaces S3 each extending from an edge of the first main surface S1 to anedge of the second main surface S2. Here, the conductive substrate CShas a flat and approximately rectangular parallelepiped shape. Theconductive substrate CS may have another shape.

The first main surface S1 is provided with first recesses R1 shown inFIGS. 3, 4, and 6 to 8 . Here, these first recesses R1 are firsttrenches each having a shape extending in the X direction as a firstdirection. As shown in FIGS. 3, 4, and 6 , the recesses R1 are arrangedin the Y direction as a second direction. A plurality of first recessesR1 may be provided or only one first recess R1 may be provided on thefirst main surface S1.

The second main surface S2 is provided with second recesses R2 shown inFIGS. 3, 5, and 6 to 8 . Here, these second recesses R2 are secondtrenches each having a shape extending in the Y direction as a seconddirection. As shown in FIGS. 3, 5, and 7 , the second recesses R2 arearranged in the X direction as the first direction. A plurality ofsecond recesses R2 may be provided or only one second recess R2 may beprovided on the second main surface S2.

A length direction of the first recesses R1 and a length direction ofthe second recesses R2 intersect each other. Here, the length directionof the first recesses R1 and the length direction of the second recessesR2 are orthogonal to each other. The length direction of the firstrecesses R1 and the length direction of the second recesses R2 mayintersect diagonally.

The “length direction” of the first or second recesses is a lengthdirection of orthogonal projections of the first or second recesses ontoa plane perpendicular to a thickness direction of the conductivesubstrate CS. Accordingly, the fact that the length direction of thefirst recesses R1 and the length direction of the second recesses R2intersect each other means that the length direction of the orthogonalprojections of the first recesses onto the plane perpendicular to thethickness direction of the conductive substrate CS intersects the lengthdirection of the orthogonal projections of the second recesses onto thisplane.

A sum of a depth D1 of the first recesses R1 and a depth D2 of thesecond recesses R2, D1+D2, is equal to or greater than a thickness T ofthe conductive substrate CS. If this configuration is adopted, the firstrecesses R1 and the second recesses R2 are connected to each other atpositions where they intersect to form through holes TH shown in FIG. 8.

A ratio of the sum D1+D2 to the thickness T, (D1+D2)/T, is preferablywithin a range of 1 to 1.4, and more preferably within a range of 1.1 to1.3. From the viewpoint of increasing the electric capacitance, theratio (D1+D2)/T is preferably large. In addition, from the viewpoint ofimproving an electrical connection between portions of the conductivelayer 20 b that are located on side walls and bottom surfaces of thefirst recesses R1 and portions of the conductive layer 20 b that arelocated on side walls and bottom surfaces of the second recesses R2, theratio (D1+D2)/T is preferably large. However, when the depths D1 and D2are increased, the mechanical strength of the capacitor 1 decreases.

Note that the ratio (D1+D2)/T may be less than 1. In this case, thefirst recesses R1 and the second recesses R2 do not form the throughholes TH shown in FIG. 8 at the positions where they intersect.Therefore, in this case, in addition to providing the first recesses R1and the second recesses R2, through holes are provided at any positionsof the substrate 10. In this case, one either or both of the firstrecesses R1 and the second recesses R2 can be omitted.

The depth D1 of the first recesses R1 and the depth D2 of the secondrecesses R2 may depend on the thickness T of the conductive substrateCS, but is within a range of 0.1 μm to 500 μm according to an example,and within a range of 1 μm to 400 μm according to another example.

It is preferable that a dimension of an opening of each of the firstrecess R1 and the second recess R2 is 0.3 μm or more. Note that thedimensions of the openings of the first recesses R1 and the secondrecesses R2 are diameters or widths of the openings of the firstrecesses R1 and the second recesses R2. Herein, the dimension of theopening of each of the first recesses R1 and the second recesses R2 is adimension in a direction perpendicular to the length directions thereof.When these dimensions are reduced, a larger electric capacitance can beachieved. However, if these dimensions are reduced, it becomes difficultto form a stacked structure including the dielectric layer 50 and theconductive layer 20 b in the first recesses R1 and the second recessesR2.

A distance between adjacent first recesses R1 and a distance betweenadjacent second recesses R2 are each preferably 0.1 μm or more. Whenthese distances are reduced, a larger electric capacitance can beachieved. However, when these distances are reduced, a portion of theconductive substrate CS sandwiched between the first recesses R1 and aportion of the conductive substrate CS sandwiched between the secondrecesses R2 are likely to be damaged.

The first recesses R1 and the second recesses R2 can have variousshapes. For example, as long as orthogonal projections of the firstrecesses R1 and the second recesses R2 onto a plane perpendicular to theZ direction intersect each other, they may each have a curved or bentshape, or may each be circular or square.

Herein, cross sections of the first recesses R1 and the second recessesR2 parallel to the depth directions are rectangular. These crosssections may not be rectangular. For example, these cross sections mayhave a tapered shape.

The through holes TH are arranged corresponding to intersections of thefirst recesses R1 and the second recesses R2. Each of the through holesTH is constituted by a part of the first recess R1 and a part of thesecond recess R2. Each of the through holes TH extends from the firstmain surface S1 to the second main surface S2. That is, each of thethrough holes TH extends in the Y direction, which is the thicknessdirection of the conductive substrate CS.

The end faces S3 of the conductive substrate CS are provided with afirst groove G1 and a second groove G2 shown in FIGS. 1 to 3 . Each ofthe first groove G1 and the second groove G2 extends from an edge of thefirst main surface S1 to an edge of the second main surface S2.

As shown in FIGS. 4 to 10 , the conductive substrate CS includes thesubstrate 10 and the conductive layer 20 a.

The substrate 10 has a shape similar to that of the conductive substrateCS. The substrate 10 is, for example, an insulating substrate, asemiconductor substrate, or a conductive substrate. The substrate 10 ispreferably a semiconductor substrate. The substrate 10 is preferably asubstrate containing silicon such as a silicon substrate. Such asubstrate can be processed using a semiconductor process.

The conductive layer 20 a is provided on the substrate 10. For example,the conductive layer 20 a is made of polysilicon doped with impuritiesto improve electrical conductivity, or a metal or alloy such asmolybdenum, aluminum, gold, tungsten, platinum, nickel, or copper. Theconductive layer 20 a may have a single-layer structure or a multi-layerstructure.

A thickness of the conductive layer 20 a is preferably within a range of0.05 μm to 1 μm, and more preferably within a range of 0.1 μm to 0.3 μm.If the conductive layer 20 a is thin, there is a possibility that adiscontinuous portion may be generated in the conductive layer 20 a, ora sheet resistance of the conductive layer 20 a may be excessivelyincreased. When the conductive layer 20 a is thickened, a manufacturingcost increases.

The conductive layer 20 a includes a first portion P1 shown in FIGS. 4to 6 and 8 , a second portion P2 shown in FIGS. 4, 5, 7, and 8 , thirdportions P3 shown in FIGS. 4 and 6 to 8 , and fourth portions P4 shownin FIGS. 5 to 8 . The first portion P1 is a portion of the conductivelayer 20 a that corresponds to the first main surface S1. The secondportion P2 is a portion of the conductive layer 20 a that corresponds tothe second main surface S2. The third portions P3 are portions of theconductive layer 20 a that are adjacent to the first recesses R1. Thefourth portions P4 are portions of the conductive layer 20 a that areadjacent to the second recesses R2.

The first portion P1 and the third portions P3 are electricallyconnected together, as can be seen from FIGS. 4, 6, and 8 . The secondportion P2 and the fourth portions P4 are also electrically connectedtogether, as can be seen from FIGS. 5, 7, and 8 . The third portions P3and the fourth portions P4 are electrically connected together at thepositions of the through holes TH shown in FIG. 8 .

In the case where the substrate 10 is a semiconductor substrate such asa silicon substrate, the conductive layer 20 a may be ahigh-concentration doped layer that is a surface region of thesemiconductor substrate doped with impurities at a high concentration.

If the substrate 10 has high electrical conductivity, the conductivelayer 20 a may be omitted, and the substrate 10 may be used as theconductive substrate CS. For example, if the substrate 10 is asemiconductor substrate made of a semiconductor doped with P-type orN-type impurities, or a metal substrate, the conductive layer 20 a canbe omitted. In this case, at least a surface region of the substrate 10,e.g. the entire substrate 10, serves as the conductive layer 20 a.

The conductive layer 20 b covers the first main surface S1, the secondmain surface S2, the end faces S3, the side walls and the bottomsurfaces of the first recesses R1, and the side walls and the bottomsurfaces of the second recesses R2. Portions of the conductive layer 20b that cover the end faces S3 may be omitted.

For example, the conductive layer 20 b is made of polysilicon doped withimpurities to improve the electrical conductivity, or a metal or alloysuch as molybdenum, aluminum, gold, tungsten, platinum, nickel, orcopper. The conductive layer 20 b may have a single-layer structure or amulti-layer structure.

The thickness of the conductive layer 20 b is preferably within a rangeof 0.05 μm to 1 μm, and more preferably within a range of 0.1 μm to 0.3μm. If the conductive layer 20 b is thin, there is a possibility that adiscontinuous portion may be generated in the conductive layer 20 b, ora sheet resistance of the conductive layer 20 b may be excessivelyincreased. If the conductive layer 20 b is thick, it may be difficult toform the conductive layer 20 a and the dielectric layer 50 withsufficient thicknesses.

The conductive layer 20 b includes a fifth portion P5 shown in FIGS. 4to 6 and 8 , a sixth portion P6 shown in FIGS. 4, 5, 7, and 8 , seventhportions P7 shown in FIGS. 4 and 6 to 8 , and eighth portions P8 shownin FIGS. 5 to 8 . The fifth portion P5 is a portion of the conductivelayer 20 b that faces the first portion P1. The sixth portion P6 is aportion of the conductive layer 20 b that faces the second portion P2.The seventh portions P7 are portions of the conductive layer 20 b thatface the third portions P3. The eighth portions P8 are portions of theconductive layer 20 b that face the fourth portions P4.

The fifth portion P5 and the seventh portions P7 are electricallyconnected together, as can be seen from FIGS. 4, 6, and 8 . The sixthportion P6 and the eighth portions P8 are also electrically connectedtogether, as can be seen from FIGS. 5, 7, and 8 . The seventh portionsP7 and the eighth portions P8 are electrically connected together at thepositions of the through holes TH shown in FIG. 8 .

In FIGS. 4 to 10 , the conductive layer 20 b is provided so that thefirst recesses R1 and the second recesses R2 are completely filled withthe conductive layer 20 b and the dielectric layer 50. The conductivelayer 20 b may be a layer that is conformal to a surface of theconductive substrate CS. That is, the conductive layer 20 b may be alayer having an approximately uniform thickness. In this case, the firstrecesses R1 and the second recesses R2 are not completely filled withthe conductive layer 20 b and the dielectric layer 50.

The conductive layer 20 b is provided with a plurality of through holes.Here, these through holes are provided in a portion of the conductivelayer 20 b that faces the first main surface S1 with the dielectriclayer 50 interposed therebetween, at positions corresponding tointersections of the second recesses R2 and regions each sandwichedbetween two adjacent first recesses R1 such that the through holes arearranged every other position in the Y direction. The conductive layer20 b may be provided with through holes at other positions. Further, theconductive layer 20 b may be provided with only one through hole.

The dielectric layer 50 is interposed between the conductive substrateCS and the conductive layer 20 b. The dielectric layer 50 is a layerthat is conformal to the surface of the conductive substrate CS. Thedielectric layer 50 electrically insulates the conductive substrate CSand the conductive layer 20 b from each other.

The dielectric layer 50 is made of, for example, an organic dielectricor an inorganic dielectric. As the organic dielectric, for example,polyimide can be used. As the inorganic dielectric, a ferroelectric canbe used. Paraelectrics, such as silicon nitride, silicon oxide, siliconoxynitride, titanium oxide, and tantalum oxide, are preferable. Theseparaelectrics have a small change in dielectric constant withtemperature. Therefore, when the paraelectrics are used for thedielectric layer 50, the heat resistance of the capacitor 1 can beimproved.

A thickness of the dielectric layer 50 is preferably within a range of0.005 μm to 0.5 μm, and more preferably within a range of 0.01 μm to 0.1μm. When the dielectric layer 50 is thin, there is a possibility that adiscontinuous portion may be generated in the dielectric layer 50, andthe conductive substrate CS and the conductive layer 20 b may beshort-circuited. Further, if the dielectric layer 50 is thinned, awithstand voltage is lowered even if there is no short circuit, and apossibility of short-circuiting when a voltage is applied is increased.When the dielectric layer 50 is thickened, the withstand voltageincreases, but the electric capacitance decreases.

The dielectric layer 50 is provided with a plurality of through holes.The through holes of the dielectric layer 50 are connected to thethrough holes of the conductive layer 20 b.

This capacitor 1 further includes an insulating layer 60 a shown inFIGS. 4 to 10 , first comb-shaped electrodes 70 a and second comb-shapedelectrodes 70 b shown in FIGS. 3 to 6 and 8 to 10 , an insulating layer60 b shown in FIGS. 4 to 10 , and a first external electrode 70 c and asecond external electrode 70 d shown in FIGS. 1 to 3, 9, and 10 .

The insulating layer 60 a faces the first main surface S1 with a part ofthe conductive layer 20 b and a part of the dielectric layer 50interposed therebetween. Specifically, the insulting layer 60 a coversthe fifth portion P5 and the seventh portions P7 of the conductive layer20 b.

The insulating layer 60 a includes a first insulating layer 60 a 1 and asecond insulating layer 60 a 2.

The first insulting layer 60 a 1 covers the fifth portion P5 and theseventh portions P7 of the conductive layer 20 b. The first insulatinglayer 60 a 1 further covers side walls of the through holes provided inthe conductive layer 20 b, and side walls of the through holes providedin the dielectric layer 50. The first insulating layer 60 a 1 is madeof, for example, an inorganic insulator such as silicon nitride andsilicon oxide.

The second insulating layer 60 a 2 covers the first insulating layer 60a 1. The second insulating layer 60 a 2 is made of, for example, anorganic insulator such as polyimide and novolac resin.

The insulating layer 60 a may have a multi-layer structure or asingle-layer structure.

The insulating layer 60 a is provided with a plurality of through holes.Some of these through holes are connected to the through holes providedin the dielectric layer 50 via the through holes provided in theconductive layer 20 b, and together with them, form second contactholes. The rest of the through holes provided in the insulating layer 60a are each provided at an intermediate position of the second contactholes adjacent in the Y direction to form first contact holes.

The first comb-shaped electrode 70 a is provided on the insulating layer60 a. The first comb-shaped electrode 70 a is an internal electrode. Thefirst comb-shaped electrode 70 a includes comb tooth portions eachextending in the X direction and arranged in the Y direction. The firstcomb-shaped electrode 70 a fills the first contact holes. The firstcomb-shaped electrode 70 a is electrically connected to the conductivelayer 20 b.

The second comb-shaped electrode 70 b is provided on the insulatinglayer 60 a. The second comb-shaped electrode 70 b is an internalelectrode. The second comb-shaped electrode 70 b includes comb toothportions each extending in the X direction and arranged in the Ydirection. The comb tooth portions of the second comb-shaped electrode70 b and the comb tooth portions of the first comb-shaped electrode 70 aare arranged alternately in the Y direction. The second comb-shapedelectrode 70 b fills the second contact holes. The second comb-shapedelectrode 70 b is electrically connected to the conductive layer 20 a.

The first comb-shaped electrode 70 a and the second comb-shapedelectrode 70 b may each have a single-layer structure or a multi-layerstructure. Each layer constituting the first comb-shaped electrode 70 aand the second comb-shaped electrode 70 b is made of a metal such ascopper, titanium, nickel, or a nickel alloy.

The insulating layer 60 b faces the first main surface S1, with a partof the conductive layer 20 b, a part of the dielectric layer 50, thefirst comb-shaped electrode 70 a, and the second comb-shaped electrode70 b interposed therebetween. Furthermore, the insulating layer 60 bfaces the second main surface S2 and the end faces S3, with another partof the conductive layer 20 b and another part of the dielectric layer 50interposed therebetween.

The insulating layer 60 b may have a single-layer structure or amulti-layer structure. A layer constituting the insulating layer 60 b ismade of, for example, an inorganic insulator such as silicon nitride, oran organic insulator such as polyimide.

The insulating layer 60 b is provided with a plurality of through holesat the positions of the first comb-shaped electrode 70 a and the secondcomb-shaped electrode 70 b. Of these through holes, one provided at theposition of the first comb-shaped electrode 70 a is a third contacthole. On the other hand, of these through holes, one provided at theposition of the second comb-shaped electrode 70 b is a fourth contacthole.

The first external electrode 70 c is provided on the insulating layer 60b. The first external electrode 70 c is electrically connected to theconductive layer 20 b via the first comb-shaped electrode 70 a.

The first external electrode 70 c includes a first bonding pad 70 c 1, asecond bonding pad 70 c 2, and a first electrode portion 70 c 3.

The first bonding pad 70 c 1 faces the first main surface S1, with apart of the dielectric layer 50, a part of the conductive layer 20 b, apart of the insulating layer 60 a, a part of the first comb-shapedelectrode 70 a, and a part of the insulating layer 60 b interposedtherebetween. The first bonding pad 70 c 1 is adjacent to an end of thefirst groove G1.

The first bonding pad 70 c 1 fills the third contact hole. The firstbonding pad 70 c 1 is electrically connected to the first comb-shapedelectrode 70 a. In addition, the first bonding pad 70 c 1 is connectedto an end of the first electrode portion 70 c 3.

The second bonding pad 70 c 2 faces the second main surface S2, withanother part of the dielectric layer 50, another part of the conductivelayer 20 b, another part of the insulating layer 60 a, and another partof the insulating layer 60 b interposed therebetween. The second bondingpad 70 c 2 is adjacent to the other end of the first groove C1. Thesecond bonding pad 70 c 2 is connected to the other end of the firstelectrode portion 70 c 3.

The first electrode portion 70 c 3 faces the end face S3, with stillanother part of the dielectric layer 50, still another part of theconductive layer 20 b, and still another part of the insulating layer 60b interposed therebetween. The first electrode portion 70 c 3 has ashape conformal to a wall of the first groove G1.

The second external electrode 70 d is provided on the insulating layer60 b. The second external electrode 70 d is electrically connected tothe conductive substrate CS via the second comb-shaped electrode 70 b.

The second external electrode 70 d includes a third bonding pad 70 d 1,a fourth bonding pad 70 d 2, and a second electrode portion 70 d 3.

The third bonding pad 70 d 1 faces the first main surface S1, with apart of the dielectric layer 50, a part of the conductive layer 20 b, apart of the insulating layer 60 a, a part of the second comb-shapedelectrode 70 b, and a part of the insulating layer 60 b interposedtherebetween. The third bonding pad 70 d 1 is adjacent to an end of thesecond groove G2.

The third bonding pad 70 d 1 fills the fourth contact hole. The thirdbonding pad 70 d 1 is electrically connected to the second comb-shapedelectrode 70 b. In addition, the third bonding pad 70 d 1 is connectedto an end of the second electrode portion 70 d 3.

The fourth bonding pad 70 d 2 faces the second main surface S2, withanother part of the dielectric layer 50, another part of the conductivelayer 20 b, another part of the insulating layer 60 a, and another partof the insulating layer 60 b interposed therebetween. The fourth bondingpad 70 d 2 is adjacent to the other end of the second groove G2. Thefourth bonding pad 70 d 2 is connected to the other end of the secondelectrode portion 70 d 3.

The second electrode portion 70 d 3 faces the end face S3, with stillanother part of the dielectric layer 50, still another part of theconductive layer 20 b, and still another part of the insulating layer 60b interposed therebetween. The second electrode portion 70 d 3 has ashape conformal to a wall of the second groove G2.

A relative position of the third bonding pad 70 d 1 with respect to thefirst bonding pad 70 c 1 is equal to a relative position of the fourthbonding pad 70 d 2 with respect to the second bonding pad 70 c 2. Here,as an example, it is supposed that an orthogonal projection of thesecond bonding pad 70 c 2 onto a plane perpendicular to the Z directionoverlaps an orthogonal projection of the first bonding pad 70 c 1 ontothis plane, and an orthogonal projection of the fourth bonding pad 70 d2 onto the aforementioned plane overlaps an orthogonal projection of thethird bonding pad 70 d 1 onto this plane.

The first external electrode 70 c and the second external electrode 70 dmay each have a single-layer structure or a multi-layer structure. Eachlayer constituting the first external electrode 70 c and the secondexternal electrode 70 d is made of, for example, a metal such asmolybdenum, aluminum, gold, tungsten, platinum, copper, nickel, or analloy containing one or more of them.

A thickness of the first external electrode 70 c and the second externalelectrode 70 d is preferably within a range of 0.1 μm to 1000 μm, andmore preferably within a range of 1 μm to 500 μm.

This capacitor 1 is manufactured, for example, by the following method.Hereinafter, an example of a method of manufacturing the capacitor 1will be described with reference to FIGS. 11 to 17 .

In this method, the substrate 10 shown in FIG. 11 is first prepared.Here, as an example, it is supposed that the substrate 10 is asingle-crystal silicon wafer. A plane orientation of the single-crystalsilicon wafer is not particularly limited, but in this example, asilicon wafer whose main surface is a (100) plane is used. As thesubstrate 10, a silicon wafer whose main surface is a (110) plane canalso be used.

Next, the through holes are formed in the substrate 10 by MacEtch(Metal-Assisted Chemical Etching).

That is, as shown in FIGS. 11 and 12 , a first catalyst layer 80 a and asecond catalyst layer 80 b each containing a first noble metal are firstformed on the substrate 10. The first catalyst layer 80 a and the secondcatalyst layer 80 b are formed so as to partially cover one main surface(hereinafter, referred to as the first surface) of the substrate 10 andthe other main surface (hereinafter, referred to as the second surface),respectively.

Specifically, a first mask layer 90 a is first formed on the firstsurface of the substrate 10.

The first mask layer 90 a is opened at positions corresponding to thefirst recesses R1. The first mask layer 90 a prevents a noble metal tobe described later from coming into contact with portions of the firstsurface that are covered with the first mask layer 90 a.

Examples of the material of the first mask layer 90 a include organicmaterials such as polyimide, fluororesin, phenol resin, acrylic resin,and novolac resin, and inorganic materials such as silicon oxide andsilicon nitride.

The first mask layer 90 a can be formed by, for example, existingsemiconductor processes. The first mask layer 90 a made of an organicmaterial can be formed by, for example, photolithography. The first masklayer 90 a made of an inorganic material can be formed by, for example,deposition of an inorganic material layer by vapor deposition, formationof a mask by photolithography, and patterning of the inorganic materiallayer by etching. Alternatively, the first mask layer 90 a made of aninorganic material can be formed by oxidation or nitriding of thesurface region of the substrate 10, formation of a mask byphotolithography, and patterning of an oxide or nitride layer byetching. The first mask layer 90 a can be omitted.

Next, the first catalyst layer 80 a is formed on regions of the firstsurface that are not covered with the first mask layer 90 a. The firstcatalyst layer 80 a is, for example, a discontinuous layer containing anoble metal. Here, as an example, it is supposed that the first catalystlayer 80 a is a particulate layer formed of first catalyst particles 81a containing a noble metal.

The noble metal is, for example, one or more of gold, silver, platinum,rhodium, palladium, and ruthenium. The first catalyst layer 80 a and thefirst catalyst particles 81 a may further contain a metal other than anoble metal, such as titanium.

The first catalyst layer 80 a can be formed by, for example,electroplating, reduction plating, or displacement plating. The firstcatalyst layer 80 a may also be formed by application of a dispersioncontaining noble metal particles, or vapor deposition such asevaporation or sputtering. Of these methods, the displacement plating isparticularly favorable because it is possible to directly and evenlydeposit the noble metal on regions of the main surface that are notcovered with the first mask layer 90 a.

Next, as shown in FIG. 12 , a second mask layer 90 b is formed on thesecond surface.

The second mask layer 90 b is opened at positions corresponding to thesecond recesses R2. The second mask layer 90 b prevents the noble metalfrom coming into contact with portions of the second surface that arecovered with the second mask layer 90 b.

As a material of the second mask layer 90 b, for example, thoseexemplified for the first mask layer 90 a can be used. The second masklayer 90 b can be formed, for example, by the same method as describedabove for the first mask layer 90 a.

Next, the second catalyst layer 80 b is formed on each of the regions ofthe second surface that are not covered with the second mask layer 90 b.The second catalyst layer 80 b is, for example, a discontinuous layercontaining a noble metal. Here, as an example, it is supposed that thesecond catalyst layer 80 b is a particulate layer formed of secondcatalyst particles 81 b containing a noble metal.

As materials of the second catalyst layer 80 b and the second catalystparticles 81 b, for example, those exemplified for the first catalystlayer 80 a and the first catalyst particles 81 a can be used. The secondcatalyst layer 80 b can be formed, for example, by the same method asdescribed above for the first catalyst layer 80 a.

It is possible that, after forming the first mask layer 90 a on thefirst main surface, the second mask layer 90 b is formed on the secondmain surface, and subsequently, the first catalyst layer 80 a is formed,and then the second catalyst layer 80 b is formed. It is also possiblethat, after forming the first mask layer 90 a on the first main surface,the second mask layer 90 b is formed on the second main surface, andafter that, the substrate is immersed in a plating solution so that thefirst catalyst layer 80 a and the second catalyst layer 80 b are formedat the same time.

Next, the substrate 10 is etched with an assist from a noble metal as acatalyst to form holes corresponding to the through holes shown in FIG.8 in the substrate 10.

Specifically, as shown in FIGS. 13 and 14 , the substrate 10 is etchedwith an etching agent 100. For example, the substrate 10 is immersed inthe etching agent 100 in liquid form to bring the etching agent 100 intocontact with the substrate 10.

The etching agent 100 contains an oxidizer and hydrogen fluoride.

The concentration of hydrogen fluoride in the etching agent 100 ispreferably within a range of 1 mol/L to 20 mol/L, more preferably withina range of 5 mol/L to 10 mol/L, and further preferably within a range of3 mol/L to 7 mol/L. When the hydrogen fluoride concentration is low, itis difficult to achieve a high etching rate. When the hydrogen fluorideconcentration is high, excess side etching may occur.

The oxidizer can be selected from, for example, hydrogen peroxide,nitric acid, AgNO₃, KAuCl₄, HAuCl₄, K₂PtCl₆, H₂PtCl₆, Fe(NO₃)₃,Ni(NO₃)₂, Mg(NO₃)₂, Na₂S₂O₈, K₂S₂O₈, KMnO₄, and K₂Cr₂O₇. Hydrogenperoxide is favorable as the oxidizer because no harmful byproduct isproduced and a semiconductor element is not contaminated.

The concentration of the oxidizer in the etching agent 100 is preferablywithin a range of 0.2 mol/L to 8 mol/L, more preferably within a rangeof 2 mol/L to 4 mol/L, and further preferably within a range of 3 mol/Lto 4 mol/L.

The etching agent 100 may further contain a buffer. The buffer contains,for example, at least one of ammonium fluoride and ammonia. As anexample, the buffer is ammonium fluoride. As another example, the bufferis a mixture of ammonium fluoride and ammonia.

The etching agent 100 may further contain other components such aswater.

When such an etching agent 100 is used, the material of the substrate10, i.e. silicon in this example, is oxidized only in regions of thesubstrate 10 that are close to the first catalyst particles 81 a or thesecond catalyst particles 81 b. Oxide generated thereby is dissolved andremoved by hydrofluoric acid. Therefore, only the portions close to thefirst catalyst particles 81 a or the second catalyst particles 81 b areselectively etched.

The first catalyst particles 81 a move toward the second surface withthe progress of etching, where etching similar to the above isperformed. As a result, as shown in FIG. 13 , at the position of thefirst catalyst layer 80 a, etching proceeds from the first surfacetoward the second surface in a direction perpendicular to the firstsurface.

On the other hand, the second catalyst particles 81 b move toward thefirst surface with the progress of etching, where etching similar to theabove is performed. As a result, as shown in FIG. 14 , at the positionof the second catalyst layer 80 b, etching proceeds from the secondsurface toward the first surface in a direction perpendicular to thesecond surface.

In this way, as shown in FIGS. 15 and 16 , recesses corresponding to thefirst recesses R1 are formed on the first surface, and recessescorresponding to the second recesses R2 are formed on the secondsurface. When a sum of the depths of these recesses is equal to or morethan the thickness of the substrate 10, these recesses are connectedtogether at positions where they intersect. In this way, the throughholes are formed at the above intersections.

In addition, at the same time as forming these recesses, recesses arealso formed on the first surface and the second surface at positionscorresponding to the first groove G1 and the second groove G2. Thereby,the through holes are formed at the positions of the substrate 10corresponding to the first groove G1 and the second groove G2.

Here, each of these through holes is circular in cross sectionperpendicular to its length direction. This cross section may have othershapes, such as a rectangle.

Thereafter, the first mask layer 90 a, the second mask layer 90 b, thefirst catalyst layer 80 a, and the second catalyst layer 80 b areremoved from the substrate 10. One or more of the first mask layer 90 a,the second mask layer 90 b, the first catalyst layer 80 a, and thesecond catalyst layer 80 b may not be removed from the substrate 10.

Next, the conductive layer 20 a shown in FIGS. 3 to 10 is formed on thesubstrate 10 to obtain the conductive substrate CS. In the case wherethe conductive layer 20 a is made of polysilicon, such a layer can beformed by, for example, LPCVD (low pressure chemical vapor deposition).In the case where the conductive layer 20 a is made of metal, such alayer can be formed by, for example, electrolytic plating, reductionplating, or displacement plating.

A plating solution is a liquid containing a salt of a metal to beplated. As the plating solution, a general plating solution, such as acopper sulfate plating solution containing copper sulfate pentahydrateand sulfuric acid, a copper pyrophosphate plating solution containingcopper pyrophosphate and potassium pyrophosphate, and a nickel sulfamateplating solution containing nickel sulfamate and boron, can be used.

The conductive layer 20 a is preferably formed by a plating method usinga plating solution containing a salt of a metal to be plated, asurfactant, and carbon dioxide in a supercritical or subcritical state.In this plating method, the surfactant is interposed between particlesof supercritical carbon dioxide and a continuous phase of a solutioncontaining a salt of a metal to be plated. That is, the surfactant isallowed to form micelles in the plating solution, and supercriticalcarbon dioxide is incorporated in these micelles.

In a normal plating method, the supply of the metal to be plated may beinsufficient in the vicinity of the bottom portions of the recesses.This is particularly noticeable when a ratio D/W of the depth D to awidth or diameter W of the recesses is large.

The micelles that have incorporated supercritical carbon dioxide caneasily enter narrow gaps. As the micelles move, the solution containinga salt of a metal to be plated also moves. Therefore, according to aplating method using a plating solution containing a salt of a metal tobe plated, a surfactant, and carbon dioxide in a supercritical orsubcritical state, the conductive layer 20 a having a uniform thicknesscan be easily formed.

Next, the dielectric layer 50 is formed on the conductive layer 20 a.The dielectric layer 50 can be formed by, for example, CVD (chemicalvapor deposition). Alternatively, the dielectric layer 50 can be formedby oxidizing, nitriding, or oxynitriding the surface of the conductivelayer 20 a.

Next, the conductive layer 20 b is formed on the dielectric layer 50.The conductive layer 20 b can be formed, for example, by the same methodas described above for the conductive layer 20 a. The conductive layer20 b is also preferably formed by a plating method using a platingsolution containing a salt of a metal to be plated, a surfactant, andcarbon dioxide in a supercritical or subcritical state.

Next, a plurality of through holes are formed in a stacked bodyincluding the conductive layer 20 b and the dielectric layer 50. Here,these through holes are formed in a portion of the above stacked bodythat is on the first main surface S1, at positions corresponding tointersections of the second recesses R2 and regions each sandwichedbetween two adjacent first recesses R1 such that the through holes arearranged every other position in the Y direction. These through holescan be formed by, for example, formation of a mask by photolithographyand patterning by etching.

Next, the first insulating layer 60 a 1 is formed on the fifth portionP5 and the seventh portions P7 of the conductive layer 20 b. The firstinsulating layer 60 a 1 can be formed by, for example, CVD.

Thereafter, the second insulating layer 60 a 2 is formed on the firstinsulating layer 60 a 1. The second insulating layer 62 a 2 is providedwith through holes at the positions of the through holes provided in theabove stacked body. When a photosensitive resin is used as the materialof the second insulating layer 60 a 2, the second insulating layer 60 a2 having the through holes can be obtained using photolithography.

Next, the first insulating layer 60 a 1 is etched using the secondinsulating layer 60 a 2 as an etching mask. Thereby, a portion of thefirst insulating layer 60 a 1 that covers the conductive layer 20 a isremoved.

Next, a first metal layer 71 and a second metal layer 72 are stacked inthis order and patterned to obtain the first comb-shaped electrode 70 aand the second comb-shaped electrode 70 b. The first comb-shapedelectrode 70 a and the second comb-shaped electrode 70 b can be formedby, for example, a combination of film formation by sputtering orplating, and photolithography.

Thereafter, the insulating layer 60 b is formed on the conductive layer20 b, the insulating layer 60 a, and the second metal layer 72. Theinsulating layer 60 b is provided with through holes at the positionscorresponding to the first comb-shaped electrode 70 a and the secondcomb-shaped electrode 70 b. The insulating layer 60 b can be formed, forexample, by the method described above for the insulating layer 60 a.

Next, the first external electrode 70 c and the second externalelectrode 70 d are formed on the insulating layer 60 b. The firstexternal electrode 70 c and the second external electrode 70 d can beformed, for example, by the method described above for the firstcomb-shaped electrode 70 a and the second comb-shaped electrode 70 b. Inthe manner described above, the structure shown in FIG. 17 is obtained.

Thereafter, this structure is diced along a line A-A. That is, thestructure is diced in such a manner that some of the dicing lines arelines of the through holes, which are provided corresponding to thefirst groove G1 and the second groove G2, extending in the X direction,and the remainders of the dicing lines are lines of the through holesextending in the Y direction.

In a structure prior to performing this dicing, it is preferable thatthe first external electrode 70 c and the second external electrode 70 dare not connected to each other at the position of the line A-A, oralternatively, the first external electrode 70 c and the second externalelectrode 70 d are connected to each other at the position of the lineA-A and are thinner at that position than the other positions. Thismakes it possible to prevent generation of undesired damage in the firstexternal electrode 70 c and the second external electrode 70 d due tothe dicing.

In the manner described above, the capacitor 1 shown in FIGS. 1 to 10 isobtained.

In this capacitor 1, the stacked structure including the dielectriclayer 50 and the conductive layer 20 b is provided not only on the firstmain surface S1 but also on the second main surface S2 and in thethrough holes TH. Therefore, this capacitor 1 can achieve a largeelectric capacitance.

In addition, in this capacitor 1, the first recesses R1 and the secondrecesses R2 are trenches. The above-described stacked structure is alsoprovided on the side walls and the bottom surfaces of the trenches.Therefore, this capacitor 1 can achieve a particularly large electriccapacitance.

In addition, in this capacitor 1, the first recesses R1 and the secondrecesses R2 intersect each other, and a sum of their depths is equal toor more than the thickness of the conductive substrate CS. Thus, whenthe first recesses R1 and the second recesses R2 are formed, the throughholes TH are generated at the positions where they intersect. Therefore,there is no need to further perform a step of forming the through holesTH in addition to the step of forming the first recesses R1 and thesecond recesses R2.

In this capacitor 1, an electrical connection between the portions ofthe above stacked structure that are located on the first main surfaceS1 and the second main surface S2 is performed using the through holesTH. Thus, both of the first comb-shaped electrode 70 a and the secondcomb-shaped electrode 70 b can be disposed on one side of the capacitor1. The capacitor 1 adopting such a configuration can be manufactured ina relatively small number of process steps.

Furthermore, this capacitor 1 makes it possible to easily increase anelectric capacitance per mounting area as will be described below.

FIG. 18 is a cross-sectional view showing an example of a capacitormodule including the above-described capacitor 1.

A capacitor module 150 shown in FIG. 18 includes a circuit substrate 110and a plurality of capacitors 1.

The circuit substrate 110 includes an insulating substrate 111 andconductor patterns 112. The circuit substrate 110 here includes theconductor patterns 112 only on its outermost surface. The circuitsubstrate 110 may be a multi-layer substrate.

Each of a plurality of capacitors 1 has the structure described withreference to FIGS. 1 to 10 . Those capacitors 1 are stacked one on topof another. The first external electrodes 70 c of two adjacent ones ofthem are electrically connected together, and the second externalelectrodes 70 d of the two adjacent ones of them are electricallyconnected together. Here, two capacitors 1 are stacked in such a mannerthat the first bonding pad 70 c 1 and the third bonding pad 70 d 1 ofone capacitor face the second bonding pad 70 c 2 and the fourth bondingpad 70 d 2 of the other capacitor, respectively. In addition, in thisstacked body, the capacitors 1 are stacked in such a manner that thefirst grooves G1 are arranged in the length direction thereof to form asingle groove, and the second grooves G2 are arranged in the lengthdirection thereof to form another single groove. These capacitors 1 arefixed to each other by an adhesive layer 130 b interposed therebetween.

This stacked body is mounted on the circuit substrate 110 in such amanner that the second bonding pad 70 c 2 and the fourth bonding pad 70d 2 of one capacitor 1 face one of the two conductor patterns 112 andthe other conductor pattern 112, respectively. This stacked body issupported by the circuit substrate 110. Here, this stacked body is fixedto the circuit substrate 110 by the adhesive layer 130 a interposedbetween the stacked body and the insulating substrate 111.

This capacitor module 150 further includes a plurality of bondingmaterials 120. These bonding materials 120 are made of, for example,conductive materials such as solder.

One of the bonding materials 120 is provided so as to be in contact withthe first electrode portions 70 c 3 of the two capacitors 1 and theconductor pattern 112. This bonding material 120 extends overapproximately the entire length of the single groove formed byconnecting the first grooves G1 of the plurality of capacitors 1. Inaddition, this bonding material 120 includes a portion positioned in agap between the first bonding pad 70 c 1 and the second bonding pad 70 c2 of adjacent capacitors 1 and a portion positioned in a gap between theconductor pattern 112 and the second bonding pad 70 c 2. According to anexample, this bonding material 120 forms a fillet. This bonding material120 ensures an electrical connection between the first externalelectrodes 70 c of the stacked capacitors 1 and an electrical connectionbetween these first external electrodes 70 c and the conductor pattern112.

The other one of the bonding materials 120 is provided so as to be incontact with the second electrode portions 70 d 3 of the two capacitors1 and the other conductor pattern 112. This bonding material 120 extendsover approximately the entire length of the single groove formed byconnecting the second grooves G2 of the plurality of capacitors 1. Inaddition, this bonding material 120 includes a portion positioned in agap between the third bonding pad 70 d 1 and the fourth bonding pad 70 d2 of adjacent capacitors 1 and a portion positioned in a gap between theconductor pattern 112 and the fourth bonding pad 70 d 2. According to anexample, this bonding material 120 forms a fillet. This bonding material120 ensures an electrical connection between the second externalelectrodes 70 d of the stacked capacitors 1 and an electrical connectionbetween these second external electrodes 70 d and the other conductorpattern 112.

In this capacitor module 150, the capacitors 1 are stacked in theirthickness direction. Accordingly, when this structure is adopted, it iseasy to increase an electric capacitance per mounting area.

In addition, in each of the capacitors 1 included in this capacitormodule 150, the first external electrode 70 c and the second externalelectrode 70 d respectively include the first electrode portion 70 c 3and the second electrode portion 70 d 3 each facing the end faces S3.Thus, for example, an electrical connection between the first externalelectrodes 70 c, an electrical connection between the second externalelectrodes 70 d, an electrical connection between the first externalelectrode 70 c and the conductor pattern 112, and an electricalconnection between the second external electrode 70 d and the conductorpattern 112 are realizable at the same time by forming the bondingmaterials 120. Accordingly, in this point also, adopting theabove-described structure makes it easy to increase an electriccapacitance per mounting area.

Furthermore, in this capacitor module 150, the capacitors 1 are stackedin such a manner that the first grooves G1 are arranged in the lengthdirection thereof to form a single groove, and the second grooves G2 arearranged in the length direction thereof to form another single groove.Thus, in the case where solder is used as the material of the bondingmaterials 120, solder melted by heating can spread over substantiallythe entire length of the above-described grooves by capillary action.Accordingly, in this point also, adopting the above-described structuremakes it easy to increase an electric capacitance per mounting area.

Second Embodiment

FIG. 19 shows a part of a capacitor according to a second embodiment.

The capacitor according to the second embodiment is the same as thecapacitor 1 according to the first embodiment except for adopting thefollowing configuration. In addition, a capacitor module according tothe second embodiment is the same as the capacitor module 150 accordingto the first embodiment except for adopting the following configurationin the capacitor.

That is, in the capacitor according to the second embodiment, one ormore first holes H1 are provided on the side walls of the first recessesR1, and one or more second holes H2 are provided on the side walls ofthe second recesses R2.

Each of the first holes H1 may be a blind hole that extends from one oftwo adjacent ones of two or more first recesses R1 and does not reachthe other. Alternatively, each of the first holes H1 may be a throughhole that connects two adjacent ones of two or more first recesses R1 toeach other. Alternatively, one or more of the first holes H1 may beblind holes, and the rest of the first holes H1 may be through holes.

Each of the second holes H2 may be a blind hole that extends from one oftwo adjacent ones of two or more second recesses R2 and does not reachthe other. Alternatively, each of the second holes H2 may be a throughhole that connects two adjacent ones of two or more second recesses R2to each other. Alternatively, one or more of the second holes H2 may beblind holes, and the rest of the second holes H2 may be through holes.

In addition, in this capacitor, the stacked structure including thedielectric layer 50 and the conductive layer 20 b is provided not onlyon the first main surface S1, the second main surface S2, and the sidewalls and the bottom surfaces of the first recesses R1 and the secondrecesses R2, but also on side walls of the first holes H1 and side wallsof the second holes H2. That is, the conductive layer 20 b further facesthe side walls of the first holes H1 and the side walls of the secondholes H2, in addition to facing the first main surface S1, the secondmain surface S2, and the side walls and the bottom surfaces of the firstrecesses R1 and the second recesses R2 with the dielectric layer 50interposed therebetween.

The capacitor according to the second embodiment can be obtained by, forexample, performing the processes for forming the first holes H1 and thesecond holes H2 in the manufacture of the capacitor 1 according to thefirst embodiment. The first holes H1 and the second holes H2 can beformed by, for example, the following method.

That is, the structure described with reference to FIGS. 15 and 16 isfirst prepared. Next, as shown in FIG. 20 , a second catalyst layercontaining a second noble metal is formed on the substrate 10 so as topartially cover the side walls of the first recesses R1 and the sidewalls of the second recesses R2.

Note that reference symbol 82 a and 82 b represent catalyst particles inFIG. 20 . As materials of the catalyst particles 82 a and 82 b, forexample, those exemplified for the first catalyst particles 81 a and thesecond catalyst particles 81 b can be used.

Next, holes corresponding to the first holes H1 and the second holes H2are formed by the MacEtch. That is, the substrate 10 is etched with anassist from a noble metal as a catalyst to form the holes correspondingto the first holes H1 and the second holes H2.

Thereafter, the conductive layer 20 a, the dielectric layer 50, theconductive layer 20 b, etc. are formed by the same method as describedin the first embodiment. In this way, the capacitor according to thesecond embodiment is obtained.

In this capacitor, the first holes H1 are provided on the side walls ofthe first recesses R1, and the second holes H2 are provided on the sidewalls of the second recesses R2. Accordingly, the conductive substrateCS of this capacitor has a larger surface area than that of a substratewith no hole provided on the side walls of the first recesses R1 and thesecond recesses R2.

In this capacitor, the stacked structure of the dielectric layer 50 andthe conductive layer 20 b is provided not only on the first main surfaceS1, the second main surface S2, and the side walls and the bottomsurfaces of the first recesses R1 and the second recesses R2, but alsoon the side walls of the first holes H1 and the second holes H2.Accordingly, this capacitor can achieve a larger electric capacitancethan the capacitor 1 with no hole provided on the side walls of thefirst recesses R1 and the second recesses R2.

The capacitor and the capacitor module according to the secondembodiment have the same effects as those of the capacitor 1 and thecapacitor module 150 according to the first embodiment, respectively.The capacitor and the capacitor module according to the secondembodiment can achieve a larger electric capacitance than the capacitor1 and the capacitor module 150 according to the first embodiment.

An average diameter of the first holes H1 is preferably 0.3 μm or more.When the diameter of the first holes H1 is reduced, more first holes H1can be arranged, thereby achieving a larger electric capacitance.However, if the diameter of the first holes H1 is reduced too much,there is a possibility that it may be difficult to form the stackedstructure of the dielectric layer 50 and the conductive layer 20 b inthe first holes H1.

A proportion of a total area of openings of the first holes H1 in anarea of a side wall of the first recess R1, which is hereinafterreferred to as an aperture ratio, is preferably within a range of 30% to90%, and more preferably within a range of 50% to 90%. In addition, aratio of the number of the first holes H1 provided on a side wall of thefirst recess R1 to an area of the side wall, which is hereinafterreferred to as a hole density, is preferably within a range of 0.4/μm²to 20/μm², and more preferably within a range of 2/μm² to 8/μm².

When the aperture ratio and the hole density are increased, a largerelectric capacitance can be achieved. However, when the aperture ratioand the hole density are increased too much, there is a possibility thatit may be difficult to form the stacked structure of the dielectriclayer 50 and the conductive layer 20 b in the first holes H1.

A distance between adjacent first recesses R1 is preferably 0.1 μm ormore, and more preferably 2 μm or more. When this distance is increased,a larger electric capacitance can be achieved. However, since a rate ofincrease in electric capacitance with respect to this distance graduallydecreases as the distance increases, it is not effective to excessivelyincrease the above distance. If this distance is increased, there is apossibility that it may be difficult to form the stacked structure ofthe dielectric layer 50 and the conductive layer 20 b in the first holesH1.

An average diameter of the second holes H2 is preferably 0.3 μm or more.When the diameter of the second holes H2 is reduced, more second holesH2 can be arranged, thereby achieving a larger electric capacitance.However, if the diameter of the second holes H2 is reduced too much,there is a possibility that it may be difficult to form the stackedstructure of the dielectric layer 50 and the conductive layer 20 b inthe second holes H2.

A proportion of a total area of openings of the second holes H2 in anarea of a side wall of the second recess R2, which is hereinafterreferred to as an aperture ratio, is preferably within a range of 30% to90%, and more preferably within a range of 50% to 90%. A ratio of thenumber of the second holes H2 provided on a side wall of the secondrecess R2 to an area of the side wall, which is hereinafter referred toas a hole density, is preferably within a range of 0.4/μm² to 20/μm²,and more preferably within a range of 2/μm² to 8/μm².

When the aperture ratio and the hole density are increased, a largerelectric capacitance can be achieved. However, when the aperture ratioand the hole density are increased too much, there is a possibility thatit may be difficult to form the stacked structure of the dielectriclayer 50 and the conductive layer 20 b in the second holes H2.

A distance between adjacent second recesses R2 is preferably 0.1 μm ormore, and more preferably 2 μm or more. When this distance is increased,a larger electric capacitance can be achieved. However, since a rate ofincrease in electric capacitance with respect to this distance graduallydecreases as the distance increases, it is not effective to excessivelyincrease the above distance. If this distance is increased, there is apossibility that it may be difficult to form the stacked structure ofthe dielectric layer 50 and the conductive layer 20 b in the secondholes H2.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

For example, in the above-described embodiments, the first comb-shapedelectrode 70 a and the second comb-shaped electrode 70 b are arranged toface one surface of the conductive substrate CS, but the firstcomb-shaped electrode 70 a and the second comb-shaped electrode 70 b maybe arranged to face each other with the conductive substrate CSinterposed therebetween.

In the above-described embodiments, the first comb-shaped electrode 70 aand the second comb-shaped electrode 70 b are provided as internalelectrodes, but the internal electrodes may have other shapes. Inaddition, the first comb-shaped electrode 70 a and the secondcomb-shaped electrode 70 b may be omitted, and the first externalelectrode 70 c and the second external electrode 70 d may be connectedto the conductive layer 20 b and the conductive substrate CS,respectively.

The first bonding pad 70 c 1, the second bonding pad 70 c 2, the thirdbonding pad 70 d 1, and the fourth bonding pad 70 d 2 may be omitted.Alternatively, the first electrode portion 70 c 3 and the secondelectrode portion 70 d 3 may be omitted.

The first recesses R1 and the second recesses R2 may be formed with suchdepths that the through holes TH are not formed. In addition, either thefirst recesses R1 or the second recesses R2 may be omitted.

Furthermore, in the above-described embodiments, the first recesses R1and the second recesses R2 are formed using MacEtch, but may be formedusing reactive ion etching (RIE).

The invention claimed is:
 1. A capacitor comprising: a conductivesubstrate having a first main surface and a second main surface, thefirst main surface being provided with one or more recesses; aconductive layer covering the first main surface and side walls andbottom surfaces of the one or more recesses; a dielectric layerinterposed between the conductive substrate and the conductive layer; afirst external electrode including first and second bonding padsrespectively facing the first and second main surfaces, the firstexternal electrode being electrically connected to the conductive layer;and a second external electrode including third and fourth bonding padsrespectively facing the first and second main surfaces, the secondexternal electrode being electrically connected to the conductivesubstrate.
 2. The capacitor according to claim 1, wherein a relativeposition of the third bonding pad with respect to the first bonding padis equal to a relative position of the fourth bonding pad with respectto the second bonding pad.
 3. The capacitor according to claim 1,wherein the one or more recesses are one or more first trenches.
 4. Thecapacitor according to claim 3, wherein one or more second trenches areprovided on the second main surface, and the conductive layer furthercovers the second main surface, and side walls and bottom surfaces ofthe one or more second trenches.
 5. The capacitor according to claim 4,wherein a length direction of the one or more first trenches and alength direction of the one or more second trenches intersect eachother, and the one or more first trenches and the one or more secondtrenches are connected to each other at intersections thereof.
 6. Thecapacitor according to claim 1, wherein the conductive substrateincludes a substrate and a conductive layer provided on the substrate,and the substrate contains silicon.
 7. A capacitor module comprising: astacked body including a plurality of capacitors stacked one on top ofanother, each of the plurality of capacitors being the capacitoraccording to claim 1, and two adjacent ones of the plurality ofcapacitors being such that the first external electrodes areelectrically connected to each other and the second external electrodesare electrically connected to each other; and a circuit substratesupporting the stacked body.